JP3292179B2 - Abnormality detection device for motor drive device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to pulse width modulation (P
The present invention relates to an abnormality detection device for a motor drive device that drives and controls an electric motor by WM) control.

[0002]

2. Description of the Related Art Conventionally, a bridge circuit having four sides each including a switching element is provided, and both ends of an electric motor are connected between a pair of terminals at diagonal positions of the bridge circuit. By connecting one terminal of the pair of terminals at the other diagonal position to the power supply line and grounding the other terminal, a power supply voltage is applied between the pair of terminals at the other diagonal position. 2. Description of the Related Art A motor drive device that controls driving of an electric motor by performing pulse width modulation control on a switching element is well known. In this type of driving device, the sum of the two terminal voltages of the electric motor is substantially “0”, that is, equal to or less than a predetermined threshold (for example,
It is also known to determine a line-to-ground fault of the electric motor when the voltage reaches about 3% of the battery voltage). (For example, JP-A-5-185937)

[0003]

However, in the above-described conventional apparatus, only the line ground fault of the electric motor is considered, and when an abnormality occurs in the motor drive device, the abnormality detection monitor device or the like, Can't cope.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to address the above problems, and has as its object to detect various abnormalities of an electric motor, a motor drive device, an abnormality detection monitor device, etc., and to widely use the electric motor. An object of the present invention is to provide an abnormality detection device for a motor drive device capable of detecting an abnormality.

In order to achieve the above object, a structural feature of the present invention is that a bridge circuit having four sides each including a switching element is provided, and a bridge circuit is provided between a pair of terminals at diagonal positions of the bridge circuit. By connecting both ends of the electric motor, and connecting one terminal of a pair of terminals at the other diagonal position of the bridge circuit to the power supply line and grounding the other terminal, the other diagonal position Applying a power supply voltage between a pair of terminals and applying pulse width modulation control to the switching element, the switching element is applied to a motor driving device that drives and controls an electric motor, based on a current flowing through the electric motor.
An operating state that determines whether the electric motor is in an operating state.
The condition determination means and the condition that the electric motor is determined to be in the operating state by the operation state determination means, the sum of the two terminal voltages of the electric motor deviated from the power supply voltage value by a predetermined value or more .
A first abnormality determining means for determining abnormality when indicating the value, operating
The state determination means determines that the electric motor is not in the operating state.
Condition, the sum of the voltage at both terminals of the electric motor
With all switching elements off
Voltage values appearing at both ends of the
When the value indicates a value that is more than a predetermined value away from the sum of
There is provided a second abnormality determining means for determining an abnormality .

[0006] In the present invention constructed as above, electrostatic
During operation of the dynamic motor (when current is flowing to the electric motor
Come), the electric motor, the motor driving apparatus, the abnormality if detected monitor device peripheral apparatus of the drive device is normal including, by the action of the bridge circuit, the terminal voltages Vm across the motor
The sum Vm of 1, Vm2 becomes substantially equal to the power supply voltage value Vb. on the other hand,
When each switching element is short-circuited, the sum Vm becomes approximately 3 · Vb / 2 or more or Vb / 2 or less. Also, when each end of the electric motor is shorted to ground (short with ground line) or shorted to power (short with power line),
The sum Vm is about 3 · Vb / 2 or more or Vb / 2 or less. Then , according to the present invention, the operating state determining means
Condition that the electric motor is determined to be operating
Meanwhile, when the sum of the two terminal voltages of the electric motor indicates a value separated from the power supply voltage value by a predetermined value or more , the first abnormality judging means judges an abnormality .
Kicking various abnormalities are detected.

[0007]

Further, in the present invention , if the peripheral devices of the electric motor including the electric motor, the motor driving device, and the abnormality detection monitoring device are normal, all the switching elements are turned off, that is, the electric motor is turned off. Working state
The terminal voltages Vm1, Vm at both ends of the electric motor
The sum Vm of m2 is a predetermined voltage. For example, if both ends of the electric motor are grounded by a pull-down resistor without connecting both ends of the electric motor to a power supply line by a pull-up resistor, the sum Vm becomes equal to the ground potential “0” (hereinafter, referred to as a first mode). ). If at least one of the two ends of the electric motor is connected to the power supply line by a pull-up resistor and at least the other end is grounded by a pull-down resistor, the sum Vm is between the power supply voltage Vb and the ground potential “0”. Is equal to a value obtained by doubling the predetermined value (the power supply voltage Vb if the values of the pull-up resistor and the pull-down resistor are equal) (hereinafter, referred to as a second mode). Furthermore, if both ends of the electric motor are connected to the power supply line by pull-up resistance without grounding both ends of the electric motor by pull-down resistance, the sum Vm becomes equal to the power supply voltage 2 · Vb (hereinafter, referred to as a third mode). ).

On the other hand, in the first aspect, when the electric motor is not operating as described above, each switching element on the power supply line side of the bridge circuit is short-circuited (short-to-power) or each end of the electric motor is closed. In the event of a short circuit (short with the power supply line), the sum Vm becomes approximately 2 · Vb.

In the second aspect, when each switching element of the bridge circuit is short-circuited while the electric motor is not operating as described above, the sum Vm becomes approximately 2 · Vb
Or it becomes "0". When each end of the electric motor is short-to-power (short-circuited with a power supply line) or grounded (short-circuited with a ground line), the sum Vm is approximately 2 · Vb or “0”. ".

Further, in the third aspect, when the electric motor is not operating as described above, each switching element on the ground side of the bridge circuit is short-circuited (ground fault) or each end of the electric motor is grounded. (Short with the ground line)
In this case, the sum Vm becomes substantially “0”.

According to the present invention , the operating state determining means
The step determines that the electric motor is not in operation.
Sum of bets on the condition, the detected sum of both terminal voltages of the electric motor, the voltage values determined in advance in a respective voltage values appearing at both ends of the electric motor on all the OFF state of the switching element If the value indicates a value that is more than a predetermined value , the second abnormality determination means determines an abnormality, so that various abnormalities in the non-operating state of the electric motor as described above are detected. As a result, according to the present invention, the operation of the electric motor
An abnormality is widely detected in the electric motor during and during the non-operation, and the abnormality can be properly dealt with.

[0013]

[0014]

[0015]

[0016]

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 schematically shows an electric power steering device for a vehicle to which a motor drive device according to the present invention is applied. .

This electric power steering apparatus includes a DC motor 10 as an electric motor. The DC motor 10 is mounted on an intermediate portion of the steering shaft 11 and rotates the coaxial 11, and applies an assist force to the steering of the front wheels by the turning operation of the steering wheel 12. The lower end of the steering shaft 11 is connected to the tie rod 14 in the steering gear box 13 so that power can be transmitted.
Are displaced in the axial direction. Tie rod 1
A front wheel (not shown) is connected to both ends of the steering wheel 4 so as to be steerable, and the front wheel is steered left and right by an axial displacement of the tie rod 14.

A steering torque sensor 21 is attached to the steering shaft 11, and the sensor 21 detects a steering torque Ts acting on the steering shaft 11, and detects the detected steering torque Ts.
Is supplied to the motor drive circuit 30. Motor drive circuit 30
Is connected to a vehicle speed sensor 22 for detecting a vehicle speed V, an engine speed sensor 23 for detecting an engine speed Ne, and a battery 24.

As shown in FIG. 2, the motor drive circuit 30 includes a bridge circuit 31 and a microcomputer 32. The bridge circuit 31 has four sides of switching elements SW1 to SW4 constituted by FETs and the like, and freewheel diodes Di1 to Di4 are connected in parallel to the switching elements SW1 to SW4, respectively. Switching elements SW1 to SW4
Is controlled on / off by each pulse train signal from the gate control circuit 33.

One of a pair of terminals at a diagonal position of the bridge circuit 31, which is a connection point of the switching elements SW1 and SW3, is connected to the battery 24 via a shunt resistor 34a and a relay switch circuit 35. ing. The other terminal, which is the connection point of the switching elements SW2 and SW4,
It is grounded via a shunt resistor 34b. Note that the resistance values of these shunt resistors 34a and 34b are set relatively small. A connection point of the switching elements SW1 and SW2 and a connection point of the switching elements SW3 and SW4, which are a pair of terminals at other diagonal positions of the bridge circuit 31, are connected to both ends of the DC motor 10, respectively, and have a pull-down resistor. Grounded via r1 and r2.

Both ends of the shunt resistor 34b are connected to a motor current detection circuit 36, which detects the DC motor 10 by the voltage appearing at both ends of the shunt resistor 34b.
The motor current Im flowing to the microcomputer 32 is detected, and the detected motor current Im is supplied to the microcomputer 32. A low-pass filter including a resistor r3 and a capacitor C1 is connected to the pull-down resistor r1, and a terminal voltage detection circuit 37 is formed by the resistors r1, r3 and the capacitor C1. The terminal voltage detection circuit 37 has a low-pass filter function as described above, and removes the high frequency component of the voltage Vm1 'at one end of the DC motor 10 and supplies the same to the microcomputer 32 as the first terminal voltage Vm1. A low-pass filter consisting of a resistor r4 and a capacitor C2 is connected to the pull-down resistor r2, and these resistors r2 and r4 and the capacitor C2
Form a terminal voltage detection circuit 38. The terminal voltage detection circuit 38 also has the low-pass filter function as described above, removes the high-frequency component of the voltage Vm2 'at the other end of the DC motor 10, and supplies the same to the microcomputer 32 as the second terminal voltage Vm2. .

The microcomputer 32 includes, in addition to the motor current Im, the first and second terminal voltages Vm1 and Vm2, a battery voltage Vb from the battery 24, a steering torque sensor 2
1, the steering torque Ts from the vehicle speed V from the vehicle speed sensor 22,
And the engine speed Ne from the engine speed sensor 23
Is also supplied. The microcomputer 32 is shown in FIG.
The program shown in (1) is repeatedly executed every predetermined short time, and the pulse width modulation (PWM) control signal is supplied to the gate control circuit 33 to control the operation of the DC motor 10; An abnormality such as 30 is detected. When the abnormality is detected, the relay switch circuit 35 is also controlled.

Next, the operation of the embodiment configured as described above will be described. When an ignition switch (not shown) is turned on, the microcomputer 24
Is supplied with a voltage, the microcomputer 32
By executing a program (not shown), it is determined whether the drive of the motor 24 may be controlled in accordance with the state of the battery 24, the DC motor 10, and the like. The switch circuit 35 is set to the ON state. Thus, the voltage from the battery 24 is supplied to the bridge circuit 31, the gate control circuit 33, and the like via the relay switch circuit 35. Hereinafter, a case where the relay switch circuit 35 is set to the ON state will be described. After setting the ON state of the relay switch circuit 35, the microcomputer 32 starts executing the program of FIG. 3 every predetermined short time.

The execution of this program is started in step 100, and the microcomputer 32 executes step 1
At 02, the engine speed Ne is input from the engine speed sensor 23, and it is determined whether or not the steering assist by the DC motor 10 is permitted based on the input engine speed Ne. If the state in which the engine speed Ne is equal to or higher than the predetermined speed has not continued for the predetermined time or longer, “NO” is determined in step 102 and the program proceeds to step 104. In step 104, the stop control of the DC motor 10, that is, the assist control by the motor 10 is stopped, and in step 134, the execution of this program ends.

If the state in which the engine speed Ne is equal to or higher than the predetermined speed has continued for a predetermined time or longer, "YES" is determined in step 102, and the program proceeds to step 106 and subsequent steps. In step 106, the first and second terminal voltages Vm are output from the terminal voltage detection circuits 37 and 38.
1, Vm2 and the first and second terminal voltages
The sum of terminal voltages Vm = Vm1 + Vm2 is calculated by adding Vm1 and Vm2. Next, at step 108, the motor current detection circuit 36
The motor current Im is input to the DC motor 10 based on whether the motor current Im is equal to or greater than a small predetermined current value Im0.
It is determined whether or not is operating. If the DC motor 10 is operating and the motor current Im is equal to or greater than the predetermined current value Im0, “YES” is determined in step 108 and the program proceeds to step 110 and subsequent steps. Further, when the DC motor 10 is in a non-operating state and the motor current Im has a predetermined current value.
If it is less than Im0 (approximately “0”), “NO” is determined in step 108 and the program proceeds to step 122 and subsequent steps.

In step 110, the DC motor 1
After clearing the second count value CT2 used for abnormality determination to “0” in the non-operation state of 0, steps 112 and 11 are executed.
At 4, it is determined whether or not the sum Vm of the terminal voltages is substantially equal to the battery voltage Vb. That is, in step 112, it is determined whether or not the sum Vm is equal to or greater than a value Vb + ΔVb obtained by adding the predetermined voltage value ΔVb to the battery voltage Vb. Also,
In step 114, the sum Vm is the battery voltage
It is determined whether or not the value is equal to or less than a value Vb−ΔVb obtained by subtracting a predetermined voltage value ΔVb from Vb. In this case, the voltage input from the battery 24 may be used as the battery voltage Vb,
A value appropriately determined in advance may be used.

If the sum Vm of the first and second terminal voltages Vm1 and Vm2 is substantially equal to the battery voltage Vb, steps 112 and 11 are executed.
In step 116, the determination is “NO”.
The count value CT1 is cleared to “0”, and the program proceeds to step 132. In step 132, the steering torque Ts is input from the steering torque sensor 21 and the vehicle speed V is input from the vehicle speed sensor 22, and the operation of the DC motor 10 is controlled in accordance with the input steering torque Ts and vehicle speed V. Specifically, the absolute value of the steering torque Ts | Ts |
DC motor 10 has an absolute value that increases as vehicle speed V increases and decreases as vehicle speed V increases, and has a direction (corresponding to positive or negative) corresponding to the direction of steering torque Ts.
Calculate the command current value I * for Then, a current equal to the command current value I * flows through the DC motor 10,
A control signal representing a pulse train signal subjected to pulse width modulation (PWM) for on / off control of each of the switching elements SW1 to SW4 is formed, and the control signal is output to the gate control circuit 33. In forming the control signal, the DC motor 10 detected by the motor current detection circuit 36 is used.
May be used as the feedback control amount.

The gate control circuit 33 outputs a pulse train signal for turning on / off each of the switching elements SW1 to SW4 to each of the switching elements SW1 to SW4 in response to the supplied control signal. In this control, when the DC motor 10 is rotated forward, the pulse train signal PWM of FIG. 4 is supplied to the switching elements SW1 and SW4, and the switching elements SW1 and SW4 are turned on and off according to the pulse train signal PWM.
The off control is performed, and the switching elements SW2 and SW3 are maintained in the off state. As a result, when the pulse train signal PWM is at the high level, the battery 24 is connected via the shunt resistor 34a, the switching device SW1, the DC motor 10, the switching device SW4, and the shunt resistor 34b as shown by a solid line in FIG. From the motor current Im to ground.
In addition, when the pulse train signal PWM is at the low level, the shunt resistor 34 shown in FIG.
b, a motor current Im flows from the ground to the battery 24 via the return diode Di2, the DC motor 10, the return diode Di3, and the shunt resistor 34a. As a result, the voltages Vm1 'and Vm2' at both ends of the DC motor 10 and the first and second terminal voltages Vm1 and Vm2 as the output voltages of the terminal voltage detection circuits 37 and 38 having a low-pass filter function are respectively shown in FIG. As shown. FIG. 4 shows the voltages Vm1 ', Vm2', Vm
1, Vm2 is conceptually exaggerated.

When the DC motor 10 is rotated in the reverse direction, the switching elements SW2 and SW3 output the pulse train signal P of FIG.
When WM is supplied, the switching elements SW2 and SW3 are on / off controlled in accordance with the pulse train signal PWM, and the switching elements SW1 and SW4 are maintained in an off state. Thus, in a state where the pulse train signal PWM is at a high level,
As shown by a broken line in FIG. 5A, a motor current Im flows from the battery 24 to the ground via the shunt resistor 34a, the switching element SW3, the DC motor 10, the switching element SW2, and the shunt resistor 34b. Also, the pulse train signal P
In the state where WM is at the low level, as shown by the broken line in FIG. 5B, the shunt resistor 34b, the return diode Di4,
The motor current Im flows from the ground to the battery 24 via the DC motor 10, the return diode Di1, and the shunt resistor 34a. As a result, the voltage Vm1 ',
Vm2 'and the first and second terminal voltages V which are the output voltages of the terminal voltage detection circuits 37 and 38 having a low-pass filter function.
m1 and Vm2 are opposite to those shown in FIG.

As described above, in the operation control state of the DC motor 10 by the pulse width modulation (PWM), the ON time and the OFF time of the switching elements SW1 to SW4 are in an inverted relationship, and the first and second switching elements of the DC motor 10 are turned over. The sum Vm (= Vm1 + Vm2) of the terminal voltages Vm1 and Vm2 is substantially equal to the battery voltage Vb. In particular, since the terminal voltage detection circuits 37 and 38 have a low-pass filter function, the sum Vm is stabilized. Then, when the program of FIG. 3 is executed again, both of them are determined to be “NO” in steps 112 and 114, so that the aforementioned steps 100, 102, 106 to 1 are performed.
The processes of 16, 132, and 134 are executed, and the turning operation of the steering wheel 12 is assisted by the DC motor 10 for steering.

On the other hand, in the operation control state of the DC motor 10, if an abnormality occurs in the motor 10, the motor drive circuit 30, and the peripheral circuits of the circuit 30, the first and second terminal voltages Vm1 and Vm2 are reduced. The sum Vm deviates from the battery voltage Vb. This abnormality is exemplified below. In this example, as shown in FIG.
Only the case where the switching elements SW2 and SW3 are maintained in the off state while the switching elements SW2 and SW3 are maintained in the off state (the solid line state in the drawing) will be described. The case where the switches SW1 and SW4 are maintained in the off state (the state shown by the broken line in the figure) is the same as the case of the abnormality of the parts having the symmetrical positional relationship in FIG. Also, the voltages Vm1 'and Vm2' at both ends of the DC motor 10, and the first and second terminal voltages Vm1
For the numerical example of the sum Vm of 1, Vm2, the switching element SW
1, Duty ratio in on / off control of SW4 is almost 5
It is assumed that it is 0%.

When the switching element SW1 is short-circuited (short-to-supply), the voltage Vm1 'at one end of the DC motor 10 is almost always Vb, and the voltage Vm2' at the other end of the motor 10 turns on the switching elements SW1 and SW4.・ Because “0” and Vb are repeated almost in synchronization with the OFF, the first and second terminal voltages Vm
The sum Vm of 1, Vm2 is approximately 3 · Vb / 2.

When the switching element SW2 is short-circuited (ground fault), the voltage Vm1 'at one end of the DC motor 10 is at most Vb / 2 and "0" at the maximum in synchronization with the on / off of the switching elements SW1 and SW4. Is repeated, and the voltage Vm2 'at the other end of the motor 10 is always substantially "0", so that the sum Vm of the first and second terminal voltages Vm1 and Vm2 is approximately Vb / 4 at the maximum.

When the switching element SW3 is short-circuited (short-to-power), the voltage Vm1 'at one end of the DC motor 10 is almost always Vb, and the voltage Vm2' at the other end of the motor 10 turns on the switching elements SW1 and SW4. -At least at the minimum, almost Vb / 2 and almost Vb are repeated in synchronization with the off state.
The sum Vm of the terminal voltages Vm1 and Vm2 is at least approximately 7 · Vb / 4.

When the switching element SW4 is short-circuited (ground fault), the voltage Vm1 'at one end of the DC motor 10 is substantially synchronized with the on / off of the switching elements SW1 and SW4.
Vb and “0” are repeated, and the voltage Vm at the other end of the motor 10 is
Since 2 ′ is almost always “0”, the first and second terminal voltages V
The sum Vm of m1 and Vm2 is almost Vb / 2.

When a short circuit occurs between the one end X1 of the DC motor 10 and the power supply line of the battery 24 (the wire harness at the other end X1 is short-to-power), the voltage at one end of the DC motor 10 is reduced.
Vm1 'is almost always Vb, and the voltage Vm at the other end of the motor 10 is
Since 2 'repeats "0" and Vb substantially in synchronization with ON / OFF of the switching elements SW1 and SW4, the sum Vm of the first and second terminal voltages Vm1 and Vm2 becomes approximately 3 · Vb / 2.

When one end X1 of the DC motor 10 has a ground fault (the wire harness at the other end X1 has a ground fault), the voltage Vm1 'at one end of the motor 10 is synchronized with the on / off of the switching elements SW1 and SW4. And the voltage Vm2 'at the other end of the motor 10 is always substantially "0" at a maximum, so that the sum V of the first and second terminal voltages Vm1 and Vm2 is obtained.
m is at most Vb / 4.

When a short circuit occurs between the other end X2 of the DC motor 10 and the power supply line of the battery 24 (the wire harness at the other end X2 is short-to-power), the voltage at one end of the DC motor 10 is reduced.
Vm1 'is almost always Vb, and the voltage Vm at the other end of the motor 10 is
2 ′ repeats at least Vb / 2 and Vb at least in synchronization with the on / off of the switching elements SW1 and SW4, so that the sum Vm of the first and second terminal voltages Vm1 and Vm2 is at least approximately 7 · Vb /
It becomes 4.

If the other end X2 of the DC motor 10 has a ground fault (the other end X2 wire harness has a ground fault), the voltage Vm1 'at one end of the DC motor 10 is synchronized with the on / off of the switching elements SW1 and SW4. And the voltage Vm2 'at the other end of the motor 10 is almost always "0", so that the sum Vm of the first and second terminal voltages Vm1 and Vm2 is substantially Vb / 2.
become.

When an abnormality occurs in the terminal voltage detection circuits 37 and 38 and the microcomputer 32, a value significantly different from Vb may be calculated as the sum Vm of the first and second terminal voltages Vm1 and Vm2. is there.

When the above-mentioned abnormality occurs during the operation of the DC motor 10, the first and second terminal voltages Vm1,
The sum Vm of Vm2 is approximately 3 · Vb / 2 or more or approximately Vb / 2 or less. Therefore, if the predetermined value ΔVb in steps 112 and 114 in FIG. 3 is set to a value smaller than Vb / 2, the above-mentioned abnormality can be detected. Specifically, a value Vb / 4 (for example, 3 volts) of about 25% of the battery voltage Vb (for example, 12 volts) may be set as the predetermined value ΔVb.

Returning to the description of the flowchart of FIG. 3 again, if any of the above-mentioned abnormalities occurs,
After the processing of steps 102 and 106 to 110, step 1
At step 12 or 114, “YES” is determined, and at step 118, “1” is added to the first count value CT1, and at step 120, the first count value CT1 becomes the predetermined value CT1.
It is determined whether it is 10 or more. If the first count value CT1 is less than the predetermined value CT10, “NO” is determined in the step 120, and the above-described assist control processing in the step 132 is executed. As a result, when only the above-described abnormality is detected suddenly, the fail process described later is not executed.

If the abnormality is not abrupt and is detected continuously, the first count value CT1 is increased every time this program is executed by the processing of step 118. If the count value CT1 becomes equal to or more than the predetermined value CT10 due to the increase of the first count value CT1, it is determined to be “YES” in step 120 and the program is executed in step 136.
Proceed to the following.

In step 136, the DC motor 1
0, the relay switch circuit 35 is turned off, a warning lamp (not shown) is turned on, and a fail process such as recording the generated abnormal state as a diagnostic code is performed. Terminate execution. In this case, unlike the processing in step 134, after the processing in step 138, this program is not executed again. In this case, only the drive processing of the DC motor 10 may be prohibited, and the program processing may be continued as usual.

As a result, the occurrence of an abnormality in the operating state of the DC motor 10 is detected, and at the same time, the assist control by the motor 10 is stopped, so that the running stability of the vehicle is ensured. In the detection of the occurrence of the abnormality, the abnormality is determined by comparing the sum Vm of the first and second terminal voltages Vm1 and Vm2 with the battery voltage Vb, so that the above-described various kinds of abnormalities can be efficiently detected. . In addition, since the abnormality determination is performed on condition that the detection of the abnormality is continued for a time corresponding to the predetermined value CT10, erroneous determination of the abnormality due to a sudden reason can be avoided, and the abnormality can be reliably determined. Can be detected.

Next, a description will be given of the abnormality determination when the DC motor 10 is not operating. In this case, the motor current
Since Im is “0”, it is determined in step 108 that “NO”, that is, the motor current Im is less than the predetermined current value Im0, and the program proceeds to step 122 and subsequent steps. After clearing the first count value CT1 to “0” in step 122, the first and second terminal voltages Vm1, Vm are determined in step 124.
It is determined whether or not the sum Vm of 2 is equal to or greater than a predetermined voltage value ΔV, that is, whether or not the sum Vm is substantially “0”.

If the sum Vm of the first and second terminal voltages Vm1 and Vm2 is substantially "0" and less than the predetermined voltage value .DELTA.V, "NO" is determined in step 124, and After clearing the second count value CT2 to “0”, the program proceeds to step 132. In step 132, the operation control process of the DC motor 10 is executed, but the motor 10 is not actually operated.
No processing for operation control is performed.

In the non-operation control state of the DC motor 10, the switching elements SW1 to SW4 are maintained in the OFF state, so that the motor 10, the motor drive circuit 30, and the peripheral circuits of the circuit 30 are normally maintained. The first and second
The terminal voltages Vm1 and Vm2 are both “0”, and the sum Vm = Vm1 + Vm2 of the first and second terminal voltages Vm1 and Vm2 is also maintained at “0”.
As a result, in this case, also when the program of FIG. 3 is executed again, “NO” is determined in the step 124, so that the above-described steps 100, 102, 10
6, 108, 122 to 126, 132, and 134 are executed.

On the other hand, if an abnormality occurs in the DC motor 10, the motor drive circuit 30, and the peripheral circuits of the circuit 30 while the DC motor 10 is not operating, the DC motor 1
The sum Vm of the first and second terminal voltages Vm1 and Vm2 of 0 deviates from “0”. This abnormality is exemplified below.

When the switching element SW1 or the switching element SW3 is short-circuited (short-to-power), the voltages Vm1 'and Vm2' at both ends of the DC motor 10 become almost Vb.
And the sum Vm of the second terminal voltages Vm1 and Vm2 is approximately 2 · Vb.

When a short circuit occurs between the one end X1 or the other end X2 of the DC motor 10 and the power supply line of the battery 24 (the wire harness of the one end X1 or the other end X2 is short-to-supply), the two ends of the DC motor 10 Voltage Vm1 ', Vm2' is almost Vb
Therefore, the sum Vm of the first and second terminal voltages Vm1 and Vm2 is approximately 2 · Vb.

When an abnormality occurs in the terminal voltage detection circuits 37 and 38 and the microcomputer 32, a value significantly different from "0" can be calculated as the sum Vm of the first and second terminal voltages Vm1 and Vm2. There is also.

When the above-mentioned abnormality occurs during the non-operation of the DC motor 10, the first and second terminal voltages Vm
The sum Vm of 1, Vm2 is no longer "0". Therefore, FIG.
If the predetermined voltage value ΔV in the step 124 is set to an appropriate small value, the above-mentioned abnormality can be detected.

Returning to the description of the flowchart of FIG. 3 again, if any of the above-mentioned abnormalities occurs,
After the processing of steps 102, 106, 108 and 122, "YES" is determined in step 124, and
At step 8, "1" is added to the second count value CT2, and at step 130, it is determined whether or not the second count value CT2 is equal to or greater than a predetermined value CT20. The second count value CT2 is the predetermined value CT2
If it is less than 0, “NO” is determined in step 130, and the above-described assist control processing in step 132 is executed. As a result, if only the above-mentioned abnormality is detected suddenly, the fail process in step 136 is not executed.

When the abnormality is not sudden and is detected continuously, the second count value CT2 is increased by the processing of step 128 every time this program is executed. If the count value CT2 becomes equal to or more than the predetermined value CT20 due to the increase of the second count value CT2, step 13
If "0" is determined as "YES", the program is executed in step 1
Proceed to 36 or later.

In step 136, the above-described fail processing is executed, and in step 138, the execution of this program is terminated. In this case, the program is not re-executed after the processing in step 138. In this case as well, only the driving process of the DC motor 10 may be prohibited, and the program process may be continued as usual.

As a result, the occurrence of an abnormality in the non-operating state of the DC motor 10 is detected, and at the time of the detection, the assist control by the motor 10 is stopped, so that the running stability of the vehicle is ensured. In the detection of the occurrence of the abnormality, the abnormality determination is performed by comparing the sum Vm of the first and second terminal voltages Vm1 and Vm2 with "0". Become. In addition, since the abnormality determination is performed on condition that the abnormality detection is continued for a time corresponding to the predetermined value CT20, it is possible to avoid an erroneous determination of an abnormality due to a sudden reason, and to reliably determine the abnormality. Can be detected.

Next, the motor drive circuit 30 of the above embodiment is described.
A modified example in which a part of the example is modified will be described. In this modification, as shown in FIG. 6, the pull-down resistor r1 of the above embodiment is omitted, and one end of the DC motor 10 is connected to the power supply line of the battery 24 via the pull-up resistor r5. The other circuit configuration is the same as the above embodiment.

Also in this modification, the bridge circuit 31
Switching element SW1, SW4 or switching element SW
2. When the DC motor 10 is operated and controlled by turning on and off the SW3, the operation is substantially the same as in the above embodiment, and the voltages Vm1 'and Vm2' at both ends of the motor 10 are substantially "0". And Vb alternately change, and the sum Vm of the first and second terminal voltages Vm1 and Vm2 also becomes substantially Vb. Then, even when an abnormality such as in the above-described embodiment occurs under the operating state of the DC motor 10,
The voltages Vm1 'and Vm2' at both ends of the motor 10 and the first and second voltages
The sum Vm of the terminal voltages Vm1 and Vm2 is the voltage value described above.

However, when the switching elements SW1 and SW4 and the switching elements SW2 and SW3 are kept off and the DC motor 10 is inactive, the voltages Vm1 'and Vm2' at both ends of the motor 10 are substantially equal to Vb. / 2, and the sum Vm of the first and second terminal voltages Vm1 and Vm2 is substantially Vb. In this case, the following abnormality detection can be performed.

When the switching element SW1 or the switching element SW3 is short-circuited (short-to-power), the voltages Vm1 'and Vm2' at both ends of the DC motor 10 are almost equal to Vb.
The sum Vm of the first and second terminal voltages Vm1 and Vm2 is approximately 2 · Vb.

When the switching element SW2 or the switching element SW4 is short-circuited (ground fault), the voltages Vm1 'and Vm2' at both ends of the DC motor 10 both become substantially "0", so that the first and second terminal voltages are changed. The sum Vm of Vm1 and Vm2 is almost “0”
Become.

When one end X1 or the other end X2 of the DC motor 10 and the power supply line of the battery 24 are short-circuited (the wire harness of the one end X1 or the other end X2 is short-to-power), both ends of the DC motor 10 Voltages Vm1 'and Vm2' are almost
Therefore, the sum Vm of the first and second terminal voltages Vm1 and Vm becomes approximately 2 · Vb.

When one end X1 or the other end X2 of the DC motor 10 is grounded (the wire harness of the one end X1 or the other end X2 is grounded), the voltage Vm across the DC motor 10 is determined.
Since 1 'and Vm2' are always substantially "0", the sum Vm of the first and second terminal voltages Vm1 and Vm2 is substantially "0".

When an abnormality occurs in the terminal voltage detection circuits 37 and 38 and the microcomputer 32, a value significantly different from Vb may be calculated as the sum Vm of the first and second terminal voltages Vm1 and Vm2. is there.

When the above-mentioned abnormality occurs in the non-operating state of the DC motor 10 as described above, the first and second terminal voltages
The sum Vm of Vm1 and Vm2 is substantially “0” or 2 · Vb. on the other hand,
When such an abnormality does not occur, since the sum Vm of the first and second terminal voltages Vm1 and Vm2 is Vb as described above,
These abnormalities can be determined by the same method as the abnormality detection when the DC motor 10 is operating, that is, by the processing of steps 106, 112 to 120 in FIG.
This eliminates the need to determine whether the motor current Im is equal to or greater than the predetermined current value Im0.

Therefore, in this modified example, the microcomputer 32 performs steps 108 and 11 in FIG.
Steps 1 to perform the processing of step 112 after step 106 while omitting the processing of 0, 122 to 130
A program consisting of 00 to 106, 112 to 120, and 132 to 138 may be executed. In this modification, the motor current detection circuit 36 is not required. As a result, according to this modification, in addition to the effects of the above embodiment, more types of abnormalities can be detected by simple processing.

This modified example is shown in FIG.
In addition to the circuit configuration of FIG. 6, one end of the DC motor 10 is grounded via the pull-down resistor r1 as in the above embodiment, and the other end of the DC motor 10 is supplied to the battery 24 via the pull-up resistor r6. It may be connected to a line. Even in this case, by executing a program similar to that of this modification, the same effect as that of this modification is expected.

Further, pull-down resistors r1 and r1 shown in FIG.
r2 may be deleted and only the pull-up resistors r5 and r6 may be left. Also in this case, the switching elements SW1, SW4 or the switching elements SW2, SW3 of the bridge circuit 31 are used.
Is on / off controlled and the operation of the DC motor 10 is controlled, the operation is substantially the same as in the above embodiment, and the voltages Vm1 ′ and Vm2 ′ at both ends of the motor 10 are substantially “0”, respectively. And Vb alternately change with each other, and the sum Vm of the first and second terminal voltages Vm1 and Vm2 is also approximately V
b. Then, even when an abnormality such as in the above-described embodiment occurs in the operation state of the DC motor 10, the voltages Vm1 'and Vm2' at both ends of the motor 10 and the first and second terminal voltages Vm1 and Vm2 are The sum Vm is the voltage value described above.

However, when the switching elements SW1, SW4 and the switching elements SW2, SW3 are kept off and the DC motor 10 is inactive, the voltages Vm1 ', Vm2' at both ends of the motor 10 are substantially equal to Vb. And the first and second
The sum Vm of the terminal voltages Vm1 and Vm2 is approximately 2 · Vb. In this case, the following abnormality detection can be performed.

When the switching element SW2 or the switching element SW4 is short-circuited (ground fault), the voltages Vm1 'and Vm2' at both ends of the DC motor 10 become substantially "0", so that the first and second terminal voltages The sum Vm of Vm1 and Vm2 is almost “0”
become.

When the one end X1 or the other end X2 of the DC motor 10 is short-circuited to the ground (the wire harness of the one end X1 or the other end X2 is grounded), the voltages Vm1 'and Vm2' at both ends of the DC motor 10 are set. Is substantially "0", and the sum Vm of the first and second terminal voltages Vm1 and Vm2 is substantially "0".

When an abnormality occurs in the terminal voltage detection circuits 37 and 38 and the microcomputer 32, a value significantly different from 2 · Vb can be calculated as the sum Vm of the first and second terminal voltages Vm1 and Vm2. There is also.

Therefore, in the case of this modification, FIG.
In the program 124, it may be determined whether or not the sum Vm of the first and second terminal voltages Vm1 and Vm2 deviates from 2 · Vb by a predetermined value or more. That is, step 12
4 is a process of determining whether or not the sum Vm is equal to or greater than a value obtained by adding a predetermined voltage value ΔVb to 2 · Vb, ie, 2 · Vb + ΔVb, as in steps 112 and 114 described above; Is a value obtained by subtracting a predetermined voltage value ΔVb from 2 · Vb, ie, 2 · Vb−
What is necessary is just to change into the process which determines whether it is less than (DELTA) Vb. The sum Vm is 2 · Vb−ΔVb <Vm <2 · Vb + Δ
When the relationship of Vb is satisfied, it is determined to be normal, and the program proceeds to step 126, where the sum Vm is Vm ≦ 2 · Vb−ΔVb or 2 ·
When Vb + ΔVb ≦ Vm, the program is determined to be abnormal, and the program proceeds to step 128. With this, the same effect as in the above embodiment is expected.

In the above-described embodiment and the modified example, the motor current Im is detected by detecting the voltage between both ends of the shunt resistor 34b. However, the detection of the motor current Im may be detected by guiding the voltage across the shunt resistor 34a to the motor current detection circuit 36. Further, a resistor is connected in series with the DC motor 10 between the connected diagonal positions of the DC motor 10 in the bridge circuit 31, and both ends of the resistor are guided to the motor current detection circuit 36 so that the motor current is detected. Im may be detected. Further, in the above-described embodiment and the modification, the motor current Im is obtained by using the voltage drop due to the resistance.
However, a non-contact type current sensor such as a Hall element may be opposed to the connection position of the resistor, that is, the position where the motor current Im flows, and the motor current Im may be detected by the sensor. .

In the above-described embodiment and the modified example, the first and second terminal voltages Vm1 and Vm2 of the DC motor 10 are used.
Are input to the microcomputer 32, and the sum Vm of the terminal voltages is calculated by the processing of step 106 (FIG. 3) of the computer 32. However, instead of this, an adder that adds the first and second terminal voltages Vm1 and Vm2 and outputs the sum Vm of both terminal voltages Vm1 and Vm2 is provided between the terminal voltage detection circuits 37 and 38 and the microcomputer 32. And the microcomputer 32 determines in step 10
6, the first and second terminal voltages Vm1,
The sum Vm of Vm2 may be input.

[Brief description of the drawings]

FIG. 1 is an overall schematic view of an electric power steering device for a vehicle to which an electric control device for an AC motor according to an embodiment of the present invention is applied.

FIG. 2 is a detailed block diagram of the drive circuit of FIG.

FIG. 3 is a flowchart of a program executed by the microcomputer of FIG. 2;

4 is a pulse width modulation (PWM) control signal PWM for switching control of the bridge circuit of FIG. 2, voltages Vm1 'and Vm2' of both terminals of the DC motor, and first and second terminals which are terminal voltage detection circuit outputs. Voltages Vm1, Vm2 and their sum Vm
It is a time chart showing.

FIGS. 5A and 5B are operation explanatory diagrams for explaining the operation of the bridge circuit of FIG. 2;

FIG. 6 is a diagram illustrating a bridge circuit and a peripheral circuit according to a modification of the embodiment.

FIG. 7 is a circuit diagram of a bridge circuit and a peripheral circuit according to another modification of the embodiment.

[Explanation of symbols]

10 DC motor, 12 steering wheel, 21 steering torque sensor, 24 battery, 31 bridge circuit, 3
2: microcomputer, 34a, 34b: shunt resistance, 36: motor current detection circuit, 37, 38: terminal voltage detection circuit, r1, r2: pull-down resistance, r5, r6
... Pull-up resistor.

Continuation of front page (56) References JP-A-5-185937 (JP, A) JP-A-7-274580 (JP, A) JP-A-5-168284 (JP, A) JP-A-5-43797 (JP) , U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H02P 6/12 B62D 5/04

Claims (1)

(57) [Claims] 1. Four sides each including a switching element
And a pair of the bridge circuits.
Connect both ends of the electric motor between a pair of terminals at
Of the pair of terminals at the other diagonal positions of the bridge circuit
Connect one terminal to the power line and the other terminal
To ground between the pair of terminals at the other diagonal positions.
Apply power supply voltage and pulse width modulate the switching element
A motor that drives and controls an electric motor by controlling
Applied to the drive,Based on the current flowing in the electric motor, the electric motor
Operating state determining means for determining whether or not the operating state; By the operating state determining means The electric motorButWorking condition
stateOn the condition that it is determined thatBoth electric motors
The sum of the terminal voltages is the power supply voltagevalueFrom the specified valueDistant values
ShowJudge when abnormalFirst abnormality determining means; The electric motor is operated by the operation state determining means.
Condition of the electric motor
The sum of the terminal voltages turned off all the switching elements
In each state, at each voltage value that appears at both ends of the electric motor
At least a predetermined value more than the sum of the predetermined voltage values
A second abnormality judging means for judging abnormality when the value indicates To
Abnormality detection for a motor drive device characterized by comprising
Output device.